Home audio & video forum: Ferrite cores - to use, or not to use?

My new Samsung plasma television (PN43E450) came with three ferrite cores (Todaisu HT2629S), a.k.a. ferrite "rings" or "collars". Instructions say I should install one on each end of power cord, providing a maximum distance from the plug (at each end) for core installed. But it doesn't say why I should install them, or if they sometimes might not be needed at all. A third ferrite core is provided for the antenna cable. Well, I don't have an "antenna," my t.v. signal arrives via AT&T's Uverse (a telephone line?). Should I treat that the same as an antenna? If the cores are always needed, why does Samsung leave it up to the consumers to install them, or not, and leave placement up to us as well? The arrangement seems to imply they are either optional or sometimes unnecessary. I searched CNET forums and found several old posts but, in each case, found no real help. Maybe I misread the tone, but in one case, a reply (by R. Proffitt) seems to come from a someone who knew the answer but felt a snarky response was all that "patshak" was due. Again, sorry if I misread the tone, but if all you intend to say is "figure it out yourself" (exact words were: "Think about or research what this part does."), then why reply at all? A follow-up by "patshak" politely ignores the attitude, and points out that using two or more of these sometimes bulky ferrite cores, let's say on adjacent lines at a power strip or outlet, can cause crowding. Okay... but this only distracts from the original query... "how does a consumer know if ferrite cores are needed?" Are there situations when using them may do more harm than good (as Proffitt implies in another answer). Perhaps ferrite cores are analogous to vitamin pills... "vitamins" are good (just like suppressing RFI)... but it they are not "one size fits all." Some of us get too much calcium, or iron, for example. I'll bet using ferrite cores, like taking vitamins, can have unintended consequences. If not, why aren't ferrite rings standard on every television power cord? Still, I cannot find any guidance for consumers on how to determine whether or not to use one or more ferrite cores. Samsung only tells consumers where, not if, the provided cores should be installed, I found no guidance on what the do or how to know if they are optional or always helpful, or only used to address a problem after it has been detected. Does Samsung provide these ferrite cores as an afterthought, maybe instead of providing a better quality (shielded) power cord? In one CNET forum thread (on ferrite cores), Proffitt writes that ferrite cores protect your "signal" from the effects of a power cord spewing radio frequency interference, but doesn't say how to determine if that is actually happening, or whether ferrite cores will help or hurt in any particular situation. Another of Proffitt's replies (to "patshak") seemed to suggest using ferrite cores on an antenna cable could harm your signal quality. If I use the three ferrite cores supplied by Samsung with my plasma television (to suppress RFI?), could they also improve or degrade the quality or quantity of power, or the signal quality delivered by any input line to my television? As an "electronics technician," I make a pretty good biologist (I am out of my field here). I suspect I am not the only one who would appreciate it if some helpful techie would explain the what, why, when and when not, and why not of using ferrite cores. Simply providing a link to a site that explains this would be fine. Won't someone who aced electrical engineering 101 give us non-techies a little guidance?

...then don't worry about using it. That's my experience around my own home as well as working with clients. If all your other devices are also working as they should, then it's a done deal. Writing en entire treatise on the merits of using ferrite cores makes no sense when you could simply do some digging on your own and come up with something quickly. Using well shielded/insulated cables is usually sufficient.

The second link ( to: "Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems" by Jim Brown (K9YC), Audio Systems Group, Inc.) was terrific. It answers all of my questions, even some I had not yet come up with.

The first link, to a wiki definition was one I had already found but still left me with questions. Thanks a bunch.

First lets examine what a ferrite cores are made of and what they are supposed to do. The ferrite core is essentially a shorted secondary winding on a transformer. Ferrite and ceramic mixtures yeild ranges across which it is most effective. Like a tuned shorted stub at microwave frequencies, the shorted wiinding can react better at different frequencies. Why use one?? In a normal environment, they are not needed but interference from harmonics can cause induced potentials in nearby wiring. Conclusion is that they should be installed, it can't hurt and may eliminate headaches later. After installation and under normal use, check the cores themselves to see if they are getting hot. They might be warm but shouldn't get hot to the touch.

Some explanatory background ("principles of electrical engineering 101") and a conclusion with not one (use it, check for heat, and but two bits of applicable advice... love it. Thanks.

But, I still have a minor concern / query. The supplied power cord has two ferrite collars assigned to it (why Samsung did not provide a power cord with these integrated ferrite beads, I have no idea). But they do provide rather precise instructions regarding placement clip around cable near plug "with 3/4 inches (20mm) maximum distance between the ferrite core and the end of the cord" inserted into TV and wall outlet.

But... there is a third ferrite collar. Instructions are to "clip it around cable as shown." The illustration shows what looks like a thin wire with a massive "plug" rather than the coaxial cable and connector of comparatively similar thickness. I have only the one end to work with (at the television) as the other end disappears through a hole in the wall. So, I will clamp it on a couple of inches away from the connector.

Having owned component audio systems since the 1960s, I am surprised to recall only having to install a ferrite core like these once before, and that was within the past couple of years. any idea why their use might be increasing?

No, no "proof." All I can offer is my admittedly questionable recollections of buying, installing and using other new electronics. I don't recall any device that came with "Do-It-Yourself" add-on ferrite cores before this Samsung plasma television. In fact, I mentioned (when starting this thread that I recalled installing one earlier, but I since realized that was something else entirely. It looked the same, but was a weight that clamped onto the kitchen sink's sprayer hose, to help the hose retract properly after each use.

So, I checked our two other televisions (both ready for disposal/recycling): neither has ferrite beads on the power cord. Neither was equipped with ferrite for our cable input line, or it would still be there. Looking further, none of our audio components have ferrite lumps (RFI protection) on their power supplies o signal-carrying lines either, despite the congested jumble of speaker wires and wires transferring signal back and forth between my receiver, CD player, DVD recorder/player, television or my (long unused) Teac tape deck.

The only visible use of ferrite RFI protection I found in our home are integrated (inseparable) ferrite beads on the power supply cords that came with our three Dell laptop computers.

Bob,Thanks for weighing in. Three TODA-ISU (part number HT2629S) "ferrite cores" (also known as ferrite beads, chokes or collars) are supplied by Samsung with their highly-rated (see CNET and Consumer Reports) plasma television (PN43E450). Samsung's ferrite devices are split cylinders, designed to clamp onto the power cord at each end, and onto the "antenna cord (not supplied)" where they are supposed to reduce radio frequency interference that would otherwise be picked up by the cables and carried into the television. However, the internal diameter (15 mm) of the ferrite devices is three times the external diameter of the designated cables (5 mm and 6 mm). The ferrite cores attach so loosely, they will not stay where installed (which, according to Samsung's specifications, must be no more than 3/4 inches from the ends of the power cord). If the physical size is far too large will it be too much impedance? Or will leaving a gap between core and cable reduce the amount of impedance (too little)? Also, as my "antenna cable" has been upgraded to a Belkin High Speed HDMI cable (a shielded cable carrying a digital signal), it is not clear that placing a ferrite core serves any purpose on that line.

If by "another ruse" you are referring to Belkin's use of the "high speed" adjective, I bought the cable for length and price. It was $19.88 plus tax, and the cheapest HDMI cable I saw on the rack. I didn't even notice "high speed" until sorting through the empty packaging, looking a model number (AV10049-12) which, interesting, Belkin's own website doesn't recognize. Getting the 43" Samsung for $377.99, and only then hearing the store would pay the $26.46 sales tax... I was so pleased, all I wanted was to go home and, if I could get the thing to fit into our cabinet, watch our new television.

If you are referring to buying the cable at any store, instead of online, you're right... They got me. It never occurred to me (until I was signing for the t.v.) that I would need a cable type I did not already own (I have spools of wire and coaxial). I did not even have to look at my wife to know I would not be dragging her to Radio Shack or KMart to see if I could save another $5 or $10, or waiting for one to come by mail.

The ferrite core is, as named, the actual magnetic CORE of an inductor, be it a transformer or a single coil, the "shorted turn" only occurs IF a turn of a separate conductor is placed around the ferrite core and the ends shorted together.The intended purpose of the cores on the power and aerial leads, is to reduce or eliminate the RF interference which may find its way into the device, in this case, the TV, and also to reduce the radiation of switch-mode noise and other interference from within the device and thus protect other devices from the TV "noise".(Try using a portable AM radio nearby to sample this noise!!)

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